Articulated vehicle



Feb. 24,1970 c, s MoNs ET AL. Re. 26,802

mncuu'rnn VEHICLE s sheets-sheet 1 Original Filed DQG. 19. 1966 F ,1970R. c. SYMONS ETAL Re. 26,802

ARTICULATED VEHICLE Original Filed Doc. 19, 1966 3 Sheets-Sheet 3 UnitedStates Patent 26,802 ARTICULATED VEHICLE Robert C. Symons and John H.Boyd, Woodstock,

Ontario, Canada, assignors to Timberjack Machines Limited, Woodstock,Ontario, Canada Original No. 3,385,389, dated May 28, 1968, Ser. No.603,011, Dec. 19, 1966. Application for reissue Sept. 27, 1968, Ser. No.765,706

Int. Cl. B62d 5/00 US. Cl. 18079.2 7 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE A steering cushioning device for anarticulated vehicle steered by a hydraulic cylinder that avoids shock asthe two vehicle frames reach the steering limits. The angle betweenframe center-lines is sensed by one or other of a pair of slidable rodsmounted on one frame and projecting into engagement with the otherframe. Rod movement is transmitted to a control valve to stop furthersteering action.

This invention relates to improvements in articulatedtype vehicles, thatis to say vehicles formed of two frames each mounted on a respectivepair of road wheels, the two frames being pivotally connected togetherabout a generally vertical axis of articulation for the purpose ofsteering the vehicle. Such vehicles are commonly used in the loggingindustry.

To steer the vehicle the angle between the frames at the axis is variedin a controlled manner. A common way of achieving this control is to usea hydraulic piston and cylinder assembly, the cylinder beingdouble-acting and being pivotally secured to one frame, while the remoteend of the piston is connected to the other frame. The line of action ofthis steering assembly is displaced laterally from the axis ofarticulation, so that expansion or contraction of the steering assemblywill have the desired steering effect. In some installations two suchpiston and cylinder assemblies may be employed. The supply of hydraulicfluid to the cylinder or cylinders is under the control of one or moresteering valves. Such valves means is typically provided with a controllevel or steering wheel which the operator moves in one direction tomodify the frame angle to steer more to the right and in the otherdirection to modify the frame angle to steer more to the left. Whencentered, the lever or wheel will neither supply fluid to each hydrauliccylinder nor allow the escape of any fluid therefrom, so that the frameangle whatever it may be will remain unchanged. Thus, if the operatormoves his steering lever or wheel into a first position and leaves it inthis position (or in the case of a spring-centered lever or wheel, holdsit in such position), the angle between the center-lines of the framewill continue to diminish on one side of the vehicle and the vehiclewill steer more and more to that side. Obviously, this articulationmovement cannot be permitted to continue indefinitely, and for thisreason it is customary to provide fixed stops on the frames to limit thesteering movement. Typically, such stops might be located so as not toallow the angle between the center-lines of the frames to be reduced oneither side to less than a value somewhere within the range of about 130to 140.

While such stops generally operate satisfactorily to limit the degree ofarticulation of the vehicle, they have the disadvantage that asubstantial shock occurs each time the stops engage each other.Considerable effort has been given to the development of stops thatwould cush- Re. 26,802 Reissuecl Feb. 24, 1970 ice ion the impact. Ruberpads, springs and hydraulic cushions have been tried, but none haveproved fully satisfactory, apart from the fact that they addconsiderably to the cost of manufacturing the vehicle. In addition theshock has undesirable effects on the hydraulic system, as will the morefully explained below.

The object of the present invention is to avoid this shock and, as aresult, both to add to operator comfort and generally to increase thelife of certain critical parts of the machine, particularly the hingepins and their bearings. Avoidance of shock would also have the effectthat hydraulic pressure surges would be reduced, which in turn wouldtend to reduce wear on the relief valves and the hydraulic systemgenerally, in a manner that will also be more fully explained below.

In addition, the installation and alignment of the comparatively heavymechanical stops that have been needed is a costly and time consumingitem in the manufacture of a vehicle of this type, and a further objectof the invention is the elimination or simplification of these stops.

Another problem encountered with conventional systems is that operatorsdo not always center the steering control when the stops make contact.To provide for this contingency, it is conventional to provide thehydraulic system with relief valves which blow off if the valve is heldin one of the steering positions after the stops have engaged. Such ablow-off action may, however, typically represent the dissipation oftwenty to thirty horsepower, which energy has to be absorbed as heat inthe hydraulic oil. Therefore, such a blow-off action if prolonged,subjects the hydraulic system to very severe service, more specifically,excess heating. Another object of the invention is the avoidance of thisdisadvantage.

To this end the invention in its preferred form consists of means forsensing reduction of the frame angle, i.e. the angle between the framecenter-lines on either side of the vehicle, to a predetermined value(namely the minimum values, say which corresponds to the maximumsteering angle desired, e.g. 45), such sensing means being connected tothe steering valve means so as in effect to center the same, as soon asthis predetermined frame angle has been reached, thus preventing anyfurther reduction of such frame angle. While in the preferred form ofthe invention the sensing means is combined with a steering mechanism ofthe type having at least one hydraulic cylinder and a hydraulic controlvalve, it will be apparent that, in its broad scope, the invention isalso applicable to other forms of steering mechanism. The essence of theinvention is to eliminate the shock of checking the frame steeringmovement by stops, and indeed normally to eliminate the need for thesestops altogether.

In the preferred form of the invention, the sensing mechanism takes theform of a pair of rods slidingly mounted parallel to each other on theframe on which the steering valve is mounted and arranged to projecttowards a plate on the other frame. This plate is so shaped that, as theframes pivot relative each other, the plate eventually comes to bearagainst the rod on the side to which the vehicle is turning. Thisaction, which becomes fully effective only as the frames near theirmaximum turning position, causes the acted-upon rod to be moved relativeto its mounting. This rod movement is transmitted to the control valvesystem to center the same, thus stopping further relative turning of theframes. This action can be made to take place gradually over the lastfew degrees of turning of the vehicle frames, so that no sudden changeof hydraulic conditions and no sudden and positive mechanical arrestingof the turning movement occurs, merely a smooth deceleration. Since therod movement actually returns the valve to its central position, theoperator is unable to hold the valve in, or move it towards, a positionthat would continue to increase the frame turning action in the samedirection.

Another advantage of the present invention arises in connection with theeffect of the vehicle striking an bstacle. For example, assume that oneend of a bulldozer blade fitted to the front of the vehicle strikes anobstacle when the vehicle is in the maximum turned condition, the end ofthe blade engaging the obstacle being such as to tend to increase theturning angle (i.e. decrease the angle between frame center-lines). Withthe conventional stops no cushioning is available and a severe shockeffect is sulTered. However, with the present invention, a cushioningeffect is available, since it is usual to provide relief valves in thehydraulic system, that will allow the steering cylinder to yieldsomewhat, and there are no stops to place an absolute limit on theturning angle. In the absence of positive stops, the vehicle is free tooversteer a few degrees in response to this type of mechanical shockload. Such oversteering will still further deflect the sensing rod,which will then act on the control valve to correct the oversteering.

It is believed that the various features and advantages of the inventionwill be better appreciated from the accompanying drawings whichillustrate various forms thereof, it being understood that the featuresof the machine illustrated are shown by way of example and not oflimitation, the broad scope of the invention being defined in theappended claims. In the drawings:

FIGURE 1 shows a fragmentary perspective view of an articulated vehiclemodified in accordance with the invention;

FIGURE 2 is a larger scale perspective view of the sensing mechanism ofFIGURE 1;

FIGURE 3 is a section on III-III in FIGURE 2;

FIGURES 4a and 4d are diagrammatic plan views of FIGURE 2, showingvarious positions;

FIGURE 5 is a central section on the control valve used in FIGURES 1 to4;

FIGURE 6 is a diagrammatic perspective view of an alternative embodimentof the invention in a first position; and

FIGURE 7 is a view similar to FIGURE 6 in a second position.

The vehicle shown fragmentarily in FIGURE 1 comprises a front frame 10and a rear frame 11 joined together by pins 12 and 13 which serve toarticulate frame members 14, 15, 16 and 17, 18, 19 together. Both frameshave a pair of road wheels 9. The steering assembly is shown simply as adouble-acting cylinder 20 and piston 21, pivotally connected by pins 22and 23 to the respective frames. Steering control valve 24 is operatedby a lever 25 by an operator who occupies seat 26. Many otherconventional parts, including casing members, have been omitted forclarity. Hydraulic hoses 27 and 28 extend to the cylinder 20, and asource of hydraulic pressure associated with the engine 29 is conveyedto the valve 24 by conduits that are not shown. The parts so fardescribed are conventional.

The sensing mechanism is better seen from FIGURE 2 and comprises a pairof detector rods 30 and 31 slidingly mounted in a bracket 32 which issecured to the front vehicle frame 10. The free ends of the rods 30, 31project towards the plate 14 for cooperation therewith, while theirother ends are pivotally connected to respective ends of a rocking bar33 that is centrally pivotally mounted at 34 on the bracket 32. Movementof the bar 33 is detected by a third rod 35 which is pivoted at one endto the bar 33 at 36. The other end of the rod 35 engages pivotally in aplate 37 (see also FIGURE 3) which is freely pivotally mounted at theend of a shaft 38. The plate 37 includes lugs 39 bearing adjustablescrews 40, the inner ends of which screws project towards a projection41 secured to the shaft 38, In this way, sliding movement of the rod 35is translated into rotational movement of the shaft 38, with a lostmotion the amount of which depends on the setting of the screws 40.

The steering lever 25 is secured to the shaft 38 to turn with it, and adownward forked projection 42 (FIGURE 5) from the lever 25 engages a pin43 at the end of a spool 44 of the control valve 24.

FIGURE 4a shows conditions with the vehicle in condition for straighttravel, i.e. the angle A between frames at 180, and with the valve lever25 in central position. FIGURE 4b shows the lever 25 pushed forward forsteering left, which action, after the lost motion has been absorbed,moves the left hand rod 31 rearwardly towards, but not into engagementwith, the plate 14. As the steering cylinder 20 turns the frames inresponse to the control valve 24 (FIGURE 4c), the plate 4 contacts therod 31 at a frame angle A. Continued turning to the left results in therod 31 being pushed back towards its original position by the plate 14.FIGURE 4d shows the steering checked condition, for which purpose therod 31 has been moved back by the plate 14 slightly beyond its originalposition, in order to center the valve 24, having regard to the lostmotion. The frames now define their minimum angle A" (say 135). Thisframe angle is the minimum normally achieved, except for any temporaryfurther reduction in the value of this angle that may take the form offorced oversteering, resulting from the vehicle striking an obstacle.Such oversteering will cause movement of the valve 24 towards the steerright condition (corresponding to backward movement of the lever 25) tocorrect the oversteer.

It is believed that it will be evident that movement from the FIGURE 4cto the FIGURE 4d position (and indeed also any oversteer beyond theFIGURE 4d position) will cause gradual movement of the control valve andhence a steady change of condition with comparatively shocklessarresting of the turning movement of the vehicle.

The control valve 24 is conventional, but for completeness has beenshown in FIGURE 5, and will now be briefly described. Pressure hydraulicfluid is received from a pump at the engine in ports 50, while port 51vents to the reservoir on the low pressure side of the pump. Outlet 52connects to hose 28, outlet 53 to hose 27. For a left turn the spool 44is removed to the left in FIGURE 5, allowing pressure fluid from theright hand port to fiow through passageways 54 to outlet 53 and thencethrough hose 27 to expand the cylinder 20. At the same time the otherend of the cylinder 20 is allowed to vent through hose 28, outlet 52 andpassageways 55 to port 51. The reverse conditions apply for a rightturn. While the drawing shows a series valve with an open-centrecircuit, there may with equal utility be used a pair of parallel valveswith closed-centre circuits.

The second embodiment shown in FIGURES 6 and 7 employs a steering wheelcontrolling a main hydraulic valve 61 to which fluid pressure fromsupply 62 can be directed to a selected one of a pair of diverter valves63, 64 and hence to a respective end of the cylinder 20. Rods 30, 31 areprovided, as before, for movement by the plate 14, although in this caseeach rod has an individual return spring 65, 66 and acts directly on arespective valve 63, 64.

FIGURE 6 shows conditions as a right turn is initiated. The wheel 60 isrotated clockwise to cause the valve 61 to admit pressure fluid fromsupply 62 through line 67, diverter valve 63 (still in normal position)and line 68, to one end of the cylinder 20 to steer the vehicle to theright. From its other end the cylinder will exhaust through line 69,valve 64, line 70, main valve 61 and line 71 to reservoir. FIGURE 7shows conditions when the desired frame angle has been reached, plate 14forcing rod 30 to actuate the valve 63 to divert the pressure fluidreceived from line 67 to line 72 which leads to the reservoir. With theparts in this position, no further steering effect is exercised on thecylinder 20, even though the wheel 60 may be held in the full right turnposition. The position of the piston 21 in the cylinder 20 is maintainedby the fact that no fluid can enter or leave the end of the cylinder 20to which line 68 is connected, since the diverter valve 63 is now closedto that line.

Steering to the left will result in the application of fluid pressure tothe cylinder 20 through lines 70 and 69, and diverter valve 64, withfinal release of such valve by the rod 31, in a manner analogous to thatalready described for a right turn.

We claim:

1. A vehicle comprising:

(a) two frames each including a pair of road Wheels,

(b) means pivotally interconnecting said frames about a generallyvertical axis of articulation.

(c) means for steering the vehicle by varying the angle between thecenter-lines of said frames at said axis,

(d) means for sensing reduction of said angle between the frames oneither side of the vehicle to a predetermined value,

(e) and means connected both to said sensing means and to said steeringmeans for acting on said steering means to prevent the same reducingsaid angle below said predetermined value, and wherein (f) said sensingmeans comprises (i) plate secured to one frame,

(ii) a bracket secured to the other frame,

(iii) and a pair of rods slidingly mounted in said bracket to projecttowards respective surfaces of said plate means located on oppositesides 3 of the vehicle,

(g) said steering means comprises (iv) at least one fluid pressureoperated doubleacting cylinder and associated piston, said piston andcylinder being connected to respective frames at a location laterallydisplaced from said axis of articulation,

(v) manually operable control valve means connected to said cylinder forselective operation of the same in either direction, and

(h) said means (e) comprises (vi) means connected to said rods fordetecting movement of either one of said rods by said plate means to anextent corresponding to reduction of said angle between the frames tosaid predetermined value on a respective side of the vehicle,

(vii) and means connecting said means (vi) to said control valve meansto move said valve means positively away from condition for steering ina respective direction, upon detection by said means (vi) of saidpredetermined value on the side of the vehicle to which said valve meanswas conditioned to steer.

2. A vehicle according to claim 1, including means for interposing anadjustable amount of lost motion in said means (vii).

3. A vehicle comprising:

(a) two frames each including a pair of road wheels,

(b) means pivotally interconnecting said frames about a generallyvertical axis of articulation,

(c) means for steering the vehicle by varying the angle between thecenter-lines of said frames at said axis,

(d) means for sensing reduction of said angle between the frames oneither side of the vehicle to a predetermined value,

(c) and means connected both to said sensing means and to said steeringmeans for acting on said steering means to prevent the same reducingsaid angle below 70 said predetermined value, and wherein (f) saidsensing means comprises (i) plate means secured to one frame,

(ii) a bracket secured to the other frame,

(iii) and a pair of rods slidingly mounted in said 75 bracket to projecttowards respective surfaces of said plate means located on oppositesides of the vehicle,

(g) said steering means comprises (iv) at least one fluid pressureoperated doubleacting cylinder and associated piston, said piston andcylinder being connected to respective frames at a location laterallydisplaced from said axis or articulation,

(v) manually operable control valve means connected to said cylinder forselective operation of the same in either direction, and

(h) said means (e) comprises (vi) a pair of check valves each connectedetween a respective end of said cylinder and said control valve meansfor diverting pressure fluid from said cylinder upon actuation of thecheck valve,

(vii) and means connecting said rods each to a respective one of saidcheck valves for actuation of the latter upon movement of either one ofsaid rods by said plate means to an extent corresponding to reduction ofsaid angle between the frames to said predetermined value on arespective side of the vehicle.

4. In a vehicle comprising:

(a) two frames each including a pair of road engaging wheels,

(b) means pivotally interconnecting said frames about a generallyvertical axis of articulation,

(c) power means for rotating said frames to and from an extreme steeringangle about said axis relatively to each other whereby to steer thevehicle, and

(d) control means movable to positions applying and discontinuingsteering power to said power means; the improvement that comprises incombination (e) an actuating member forming a part of said control meansand movable to control normally the steering positions of said frameswhile said frames rotate through a major part of their extreme steeringangle, and

(f) further means responsive to rotation of said frames for moving saidcontrol means when said frames rotate to a steering position beyond saidmajor part of the extreme angle, and including a portion acting onlywhen said frames so rotate for moving said control means to a positiondiscontinuing the steering power, so as to reduce power loss due toextreme steering while permitting the actuating member its normalcontrol of the steering positions of the frames.

5. In a vehicle comprising:

(a) two frames each including a pair of road engaging wheels,

(b) means pivotally interconnecting said frames about a generallyvertical axis of articulation,

(c) power means for rotating said frames to and from an extreme steeringangle about said axis relatively to each other whereby to steer thevehicle, and

(d) control means movable to positions applying and discontinuingsteering power to said power means; the improvement that comprises incombination (e) a manual steering handle forming a part of said controlmeans and movable to control normally the the steering positions of saidframes while rotating through a major part of their extreme steeringangle,

(f) sensing means associated with said frames for offering a particularresponse only when said frames rotate to a steering position beyond saidmajor part of the extreme angle, and

(g) connecting means through which said sensing means apply theirparticular response for moving said control means to a positiondiscontinuing the application of steering power to said power means, soas to reduce power loss due to extreme steering while permitting thesteering handle its normal control of the steering positions of theframes.

6. The combination as set forth in claim 5, in which said power meansinclude a hydraulic steering ram interconnecting the two vehicle frames,said control means comprising valve means that control fluid pressuresdirected to said ram, and said steering handle and said sensing meansbeing connected each to a part of said valve means for moving that partof the valve means.

7. The combination as set forth in claim 6, in which said sensing meansinclude a member mounted for movement on one of the vehicle frames andengaging said connecting means, and a portion of said member normally inspaced relation to the other of said frames and References Cited UNITEDSTATES PATENTS 2,614,644 10/1952 Guslafson 18079.2 2,896,734 7/1959 TOth18079.2 3,312,301 4/1967 Hagen 18079.2

BENJAMIN HERSH, Primary Examiner J. A. PEKAR, Assistant Examiner US. Cl.X.R.

engaged by said other frame when the frames rotate 15 6052; 74-388beyond said substantial stering angle.

